The present invention relates to a metering valve for use in sanitary installations. More particularly, the present invention relates to a self-closing valve assembly with reduced operating effort and improved ability to maintain a timed flow of water despite variations in water supply pressure and temperature.
Metering valves for lavatory applications are generally used in commercial or public buildings. Metering valves are intended to provide a flow of water for a predetermined period of time when they are actuated. Typically, a metering valve is mounted on, for example, a faucet in a public restroom and actuated by pressing down on a handle. When the handle is released, water is supposed to flow for a preset time to allow the user to wash up. After the preset time, the metering valve completely shuts off the water.
Several existing metering valves use a washer compression valve as the main water flow control valve. Washer compression valves use the inlet water pressure to assist in sealing. The force of the inlet water pressure must then be overcome to open the valve. Because of this direct dependence on inlet water pressure, these types of metering valves are often very sensitive to changes in water pressure and are thus prone to large swings in operating effort necessary to begin water flow as well as swings in cycle time once the valve is actuated. The operating effort necessary to actuate a metering valve used in public buildings is preferably five pounds or less under the Americans with Disabilities Act (ADA).
In order to control the cycle time of the metering valve, various valve configurations have been attempted in the industry. U.S. Pat. No. 4,899,778 discloses a metering valve that uses handle stroke and a very small diameter pilot hole to control cycle time. This design can lead to cycle times that are very dependent upon inlet water supply pressure. Also, the small pilot hole can be easily clogged. The metering valve disclosed in U.S. Pat. No. 3,933,337 discloses another approach to maintaining a desired cycle time through the use of a sealed damping chamber containing a special timing fluid. This design can be disadvantageous because small amounts of the timing fluid may be lost with each cycle. Also, any type of timing fluid with a higher viscosity than water will increase operating effort and be sensitive to water temperature changes.
Accordingly, there is a need for a metering valve with an operating effort that is less sensitive to water supply pressure and temperature, a cycle time that is not significantly affected by water supply pressure and temperature, and improved resistance to mineral or particulate contamination in the water supply.